Hollow vessels made of a polyolefin resin, such as polypropylene resin, are, in general, superior in the stiffness, heat resistance and chemical resistance, nevertheless they reveal usually disadvantages of lower transparency and inferior impact resistance. For remedying these disadvantages, polyolefinic resins in which these inferior properties are improved have been brought into practical use. Proposals for such improved polyolefinic resins include, for example, a resin composition in which a linear polyethylene and an elastomer component are blended with a polypropylene resin (Japanese Patent Kokai Sho 61-98756 A), a resin composition in which a polymerization product of ethylene is blended with a polypropylene resin (Japanese Patent Kokai Hei 6-31796 A), a resin composition in which a polymerization product of 3-methylbutene-1 is blended with a polypropylene resin (Japanese Patent Kokai Hei 3-14852 A, corresponding to U.S. Pat. No. 5,286,540 and to EP 417319 A1) and a resin composition in which a specific nucleation enhancing agent is blended with a polypropylene resin (Japanese Patent Kokai Sho 60-127336, corresponding to EP 151741 A2).
Hollow vessels made of conventionally proposed polyolefin resins such as above have problems, that an improvement in the impact strength may accompany a decrease in the transparency and that an improvement in the transparency may cause unpleasant smell or may cause decrease in the impact strength. Moreover, it is also problematic that hollow vessels of prior art are subject to decrease in the transparency upon a heat sterilization with saturated steam, whereby visibility of the contents retained in the vessel, such as a drink or medical goods, is decreased and their state becomes unrecognizable.
When a nucleation enhancing agent is blended in the resin of the vessel for improving the transparency of the vessel, the productivity of the vessel becomes decreased due to high crystallization rate, in addition to an unfavorable consequence that such an additive may often cause emission of unpleasant smell and is not preferred for such hollow vessels. Especially, in the case of hollow vessels to be served for enclosing medical goods and food products therein, such problems as emission of smell and migration of the additive from the resin of the vessel into the contents thereof are the greatest defect. When a resin composition in which an ethylenic polymer is blended with a polypropylene resin for improving the impact strength is used as the material of the hollow vessel, an increase in the amount of the ethylenic polymer for increasing the impact strength will cause decrease in the transparency, so that hollow vessels having satisfactory properties may scarcely be reached.